Origins of Hawai'i

The Island Building Process—Origins of the Hawaiian-Emperor Chain

Dynamic and ever changing, the Hawaiian Islands are just the most recent products of the Hawaiian magmatic hot spot, a stationary plume of magma (molten lava) rising from deep in the Earth. During the last 75 to 80 million years, the Hawaiian hot spot has created at least 107 volcanoes that now span over the Pacific seafloor for more than 3,100 miles (4,990 km), and are known as the Hawaiian-Emperor Chain.

The volcanoes of the Hawaiian-Emperor Chain were formed as a piece of the Earth’s crust known as the Pacific Plate (a tectonic plate) drifted on the molten rock (magma) beneath it.

As the Pacific Plate moved over the stationary magmatic hot spot, magma erupted up through the Pacific Plate creating volcano after volcano. The Pacific Plate has been moving continuously over the erupting hot spot for the last 80 million years.

As the magma of the hot spot burned up through the Earth’s crust, it piled layer upon layer of lava onto the ocean floor. This lava built an underwater volcano to heights of ten, fifteen, twenty thousand feet until finally, in a fitful burst of steam and liquid stone, the volcano reached the ocean’s surface and became an island.

After each volcanic island was created above the active hot spot lava plume, it was then rafted northwest at the rate of about 3½ inches (9 cm) per year, making way for the next volcano to emerge.

Over millions of years, island after island was formed, and each in turn was carried northwest away from the magmatic hot spot by the movement of the Pacific Plate. These volcanic islands first became dormant and then extinct as they moved northwest away from the magmatic hot spot.

The volcanic island building process continues today on the island of Hawai‘i at the southeast end of the Hawaiian Island Chain, where Kīlauea Volcano is currently above one edge of the Hawaiian hot spot’s actively erupting lava. The other edge of the erupting lava plume is beneath the sea about 18 miles (29 km) off Hawai‘i Island’s southeast coast, where it has formed a seamount called Lō‘ihi. This undersea volcano continues to grow, and is already 9,000 feet (2,750 m) tall with about 3,200 feet (975 m) to go before it reaches the ocean’s surface and then rises above to become the next Hawaiian Island.

The island of Hawai‘i (the Big Island) is the most recently formed Hawaiian Island, at less than one-half million years old. Like Lō‘ihi Seamount, the island of Hawai‘i also continues to grow, its size having increased by more than 370 acres (150 ha) since 1984 when Kīlauea Volcano erupted fiery fountains of lava to heights of over 1,500 feet (460 m). From 1983 to the present, Kīlauea Volcano has been erupting almost continuously.

[Photograph: Erupting lava]

Kaua‘i is the northernmost and oldest of the eight main Hawaiian Islands, having first risen above the sea more than five million years ago. Kaua‘i’s highest peaks were once thousands of feet taller, but centuries of tropical rainstorms have eroded the heights of Kaua‘i’s volcanic summits.

The ancient volcanoes of the Northwestern Hawaiian Islands have also been eroded away by the effects of rain, wind, waves, and time. The 124 small islets, atolls and shoals of the Northwestern Hawaiian Islands span over more than 1,000 miles (1,600 km) of ocean, beginning hundreds of miles northwest of the eight main Hawaiian Islands. Most of the tiny islets barely rise above the water’s surface.

Some millions of years from now, Kaua‘i will also have eroded down to sea level, first leaving an atoll and then finally disappearing once again beneath the sea.

[Photograph: Cliffs and spires of Nāpali Coast]